1. Field of the Invention
The invention relates to a semiconductor device, and in particular, to a semiconductor device used as a switching element of a power circuit.
2. Description of the Related Art
In recent years, as electronic apparatuses such as personal computers and mobile phones are miniaturized, electronic components have been mounted in high density, and for this reason, various researches are ongoing in order to reduce a mounting area of a semiconductor device such as a diode or a transistor. Among such semiconductor devices, a switching MOSFET, which is used as a load switch to switch a power source such as a battery, is required to improve a heat dissipation efficiency and to reduce on-resistance in addition that it is required to make it small and thin.
In consideration of the above, a technique, in which the shape of a main pad on which a semiconductor chip is to be mounted is changed, has been proposed (for example, see U.S. Pat. No. 6,242,800).
FIG. 11(a) is a top view showing a conventional semiconductor device, FIG. 11(b) is a cross-sectional view taken along the line A-A of FIG. 11(a), and FIG. 11(c) is a side view showing the semiconductor device of FIG. 11(a). As shown in FIG. 7, a lead terminal protruding outward from the resin package has been a gull wing type one, which is bent downward along the side surface of the package.
Next, a structure of the semiconductor device according to the related art will be described. A semiconductor chip 1 is mounted on a main pad 2 upside down. The main pad 2 is integrated with leads 3, 4, 5, and 6. First and second surface leads 7 and 8 are separated from the main pad 2 to protrude outward from a resin package 9. The first surface lead 7 and a source electrode 10 are wire-bonded through a plurality of wires 11. Similarly, the second surface lead 8 and a gate electrode 12 are wire-bonded through a wire 13. A surface of a semiconductor chip 11 being in contact with the main pad 2 includes a drain electrode.
According to the above-mentioned structure, the semiconductor chip is mounted on a lower surface of the main pad, so that it is possible to make a semiconductor device thin. Also, the drain electrode is mounted on the main pad having a large area, so that it is possible to achieve excellent heat dissipation efficiency.
Recently, in a portable apparatus, such as a mobile phone using a battery as a power, a problem to be solved is to reduce power consumption in electronic components including a semiconductor device mounted inside the apparatus in order to increase the power capacity available by charging one-time, in addition to making the apparatus thin and have high functionality.